This dissertation deals with the struggles faced by mothers of victims of Brazilian state violence. More specifically, about the political engagement of mothers, slum dwellers in Rio de Janeiro, who have lost their sons murdered by military police and state agents. The reflections I brought to the fore are the results of an ethnographic project in which I followed and witnessed the public mourning of some mothers in the public space of the city. Through witnessing their mourning I was able to develop the problematic tackled in this thesis: the relationship between gender, violence, sovereignty and sacrifice. Based on my ethnographic experiences, I argue that the movement organized by these mothers put into question the legitimacy of state sovereignty, in other words its power over life and death. When they claim that the Brazilian state did not have the right to take their sons lives, lives which they give birth to, they bring to the fore the intimate relation between gender and sovereignty. In addition, I argue that the mothers movement touch upon the foundational structures of the nation-state when they reveal the state sovereignty reliance on an economy of sacrifice, specifically one in which the lives of some depend on the death of others. The mothers movement provides the conditions both to expose the sacrificial logic upon which state sovereignty relies and to reveal that the mothers themselves are also embedded in a sacrificial economy when they struggle in the name of their sons killed by the state. In this sense, my thesis is a philosophical investigation in order to grasp the mythological foundations of state sovereignty and its intrinsic reliance of an economy of sacrifice.